The present invention is directed to a method for implanting a patellar prosthesis in a human patella.
In total knee replacement surgery, a prosthesis is provided in which one component is fastened to the distal end of the femur which has been resectioned and another component is fastened to the proximal end of the tibia which has been resectioned so that the two components will act together in permitting the leg to bend and straighten out. In performing such surgery, the patella is not normally replaced but rather is resected such the interior crown portion facing the condyles is cut and reamed to form a cavity in which a patellar prothesis is implanted. The patellar prosthesis has a crown facing inwardly to engage the patellar or trochlear groove of the femoral component.
Heretofore, in preparing a patella for an implant, it was necessary to engage the patella with a clamp having a circular cross-sectional configuration and, using the interior surface of the clamp as a guide, ream a cavity in the patella of sufficient size to receive the patellar implant intended to be used. Depending upon a number of factors including the size of the patient, the patellar implant could be one of a number of different sizes. As a result of this, it was necessary to have available a number of clamps each having a different diameter for guiding various size reamers. Typical prior art methods of forming a cavity for implanting a patellar prosthesis are shown and described in the following publications, which are incorporated herein by reference: Brochures entitled "The AMK Total Knee System Design Rationale and Surgical Procedure" (page 25), DePuy, Division of Boehringer Mannheim Corporation, Warsaw, Ind, and "WHITESIDE ORTHOLOC a Modular KNEE SYSTEM", copyright 1989 by Dow Corning right, Arlington, Tenn. Copies of such references are herewith enclosed.
There has recently been introduced a new design of patellar prosthesis having a tapered surface on the side away from the crown. One such prosthesis is the subject matter of U.S. patent application Ser. No. 07/508,088, filed Oct. 18, 1990, by the applicant herein. The present method for implanting a patellar prosthesis is well-suited for implanting patellar prostheses of the type disclosed in such patent application; however, it should be understood that the method of the present invention is not so limited and may be used for implanting a wide variety of patellar prostheses. It has a significant advantage over the prior art for implanting a patellar prosthesis of a type in which one of a number of different sizes is to be used depending upon the patient in that the method of the present invention does not rely upon the patella clamp to guide the reamer. Accordingly, in utilizing the method of the present invention, it is not necessary to have available a plurality of clamps of varying sizes.